Optical fiber networks such as optical rings are commonly used in communication systems. Examples of optical fiber rings include unidirectional path switch rings and bi-directional line switch rings. Switching nodes may also be connected in a mesh topology, as in known, and such networks are typically referred to as mesh networks.
FIGS. 1a and 1b illustrate a bi-directional line switch ring 100 with five switching nodes. The five switching nodes are respectively labeled as A, B, C, D, and E. A fiber span consisting of a working fiber (or pair of fibers) and a protection fiber (or pair of fibers) are provided between any two adjacent nodes. In the figures, dashed lines represent protection fiber, while solid lines represent working fiber.
In FIG. 1a, a network connection 101 is established from switching node B to switching node E, and a network connection 102 is established from switching node E to switching node B. Network connection 101 traverses working fibers 120, 130, and 140. Network connection 102 traverses through working fibers 150 and 110.
Conventional BLSR networks such as the one shown in FIG. 1a utilize the same channel to transmit the network connection around the ring. For example, a first channel would be used to transmit the network connection 101 along the working fibers. If a protection switch event occurs, another channel would be used to transmit the network connection along the protecting fibers but in both cases a single channel is used for the network connection as it traverses the working fibers and a single channel is used for the protecting fibers.
FIG. 1b illustrates that network connection 101 traverses a different path when a span failure occurs between switching nodes C and D. When the span between switching nodes C and D fails, switching node C performs a line switching operation as known in the art to connect working fiber 120 with protection fiber 125, and switching node D performs a line switching operation to connect protection fiber 145 with working fiber 140. After the span failure, the network data traveling from node B to node E on network connection 101 traverses working fiber 120, protection fibers 125, 115, 155, 145, and working fiber 140.